While at Beth Israel Medical Center (2000 - 2014), Dr. Poretsky served as Chief of the Division of Endocrinology, Vice-Chairman for Research, and Interim Chairman in the Department of Medicine. He held the Gerald J. Friedman endowed chair in endocrinology and metabolism at Beth Israel Medical Center and was a founding director of the Gerald J. Friedman Diabetes Institute.[6]

Gerald J. Friedman Diabetes Institute is an education, clinical management and research program focused on diabetes which requires no insurance or physician referral. At the institute Poretsky chairs the annual Friedman Fellows Symposia, which present the work of fellows from around the US supported by The Gerald J. and Dorothy R. Friedman New York Foundation for Medical Research.[1][9]

In September 2014, Dr. Poretsky joined the staff of Lenox Hill Hospital as its Chief of the Division of Endocrinology. He is leading the effort to develop academic and clinical programs. An endocrinology fellowship program was initiated in July 2016 and a new site for the Gerald J. and Dorothy R. Friedman Diabetes Institute at Lenox Hill Hospital opened on August 1, 2016. As of August 2016, the division has 7 grants, including two from a philanthropic organization (The Gerald J. and Dorothy R. Friedman New York Foundation For Medical Research), two from industry (Sanofi, Inc., and Novartis Pharmaceutical Corp.) and three from the government agencies (two from New York State Department of Health and one from the National Institutes of Health). Lenox Hill Hospital is a part of Northwell Health, formerly North Shore – LIJ Health System, a network of hospitals, nursing homes, a medical school, a nursing school, a medical research institute, ambulatory care centers, urgent care centers, a health insurance company, and laboratories.

Dr. Poretsky has regularly appeared in the New York Times Magazine Best Doctors List and the U.S. News & World Report Best Doctors List.[6]

He contributed to and edited the comprehensive textbook Principles of Diabetes Mellitus, which has been widely cited,[10] and has gone through three editions so far (2002, 2010 and 2017[10][11][12]). The book covers a wide range of topics on diabetes.[10][11][12]

In 2012 he edited Diabetes Mellitus: A Concise Clinical Guide, which covers "the basics of diagnosis, complications, therapies and prevention of diabetes." The book consists of sections originally published in the second edition of Principles of Diabetes Mellitus.[13]

He is also a series editor for “Contemporary Endocrinology”.[2] (Springer, Inc.)

Poretsky has been vocal in the media about how health care policy can affect patient care. In the 1990s he wrote a letter to the editor of New York Times concerning how Medicaid payment caps can limit physicians' availability to patients.[14] In July 2012 he wrote an op-ed for Forbes which drew comparisons between the bureaucratic behavior of the American healthcare system and that of the Soviet Union's, which he says "collapsed under the weight of its own bureaucratic inefficiencies two decades ago."[15] This article was followed by a scholarly publication on the subject entitled “The sovietization of American medicine: Notes from the front lines”, which appeared in Journal in American Physicians and Surgeons, 2013.[16]

In 2013 he published a letter in the Wall Street Journal talking about inadequate methods used by the government to assess hospital performance[17] and a letter regarding policy changes needed to reduce hospital readmissions.[18] In 2017, he published a letter about Medicare being allowed to complete with private health insurance plans.[19]

While working as a research fellow at Harvard in the early 1980s, Poretsky became known for discovering, describing and characterizing insulin receptors in the human ovary.[20]

Before his research, the hormone insulin had been known to primarily regulate glucose and other fuel metabolism in the liver, fat, and muscle.[20] His work established the ovary as a target for regulation by insulin, and introduced a new paradigm for the gonadotropic function of insulin.[21]

Poretsky had been researching the causes of hyperandrogenism (high level of male hormones and male features in females) in patients with extreme forms of insulin resistance, for example in people with insulin receptor gene mutations.[20] Subsequently, Poretsky’s work became important for understanding more common disorders, such as polycystic ovary syndrome (PCOS), which affects up to 10% of reproductive age women and is associated with infertility and diabetes.[22] Poretsky’s work helped lead to the use of insulin-sensitizing agents in patients with PCOS.[23][24]

Poretsky and his coworkers also characterized related receptors in the ovary (insulin-like growth factor receptors,[25]peroxisome-proliferator activated receptor-gamma),[26][27] and he conceptualized an insulin-related ovarian regulatory system.[1]

Another line of Poretsky's research involved endocrine manifestations of acquired immunodeficiency syndrome (AIDS), and includes an early review of endocrinological dysfunction in AIDS patients.[28]

Additionally, in 1987 Poretsky was a key member of the team which described a condition called hyporeninemic hypoaldosteronism, which is characterized by deficiency of adrenal hormone aldosterone, in patients with AIDS. This discovery resulted in introduction of treatment with fludrocortisone, which proved to be extremely effective and almost immediately converted most patients with this condition from being unable to stand (because of a severe drop in blood pressure upon standing) to being mobile and more functional.[2]

Poretsky was also key in first describing a type of inflammation of the thyroid (thyroiditis) which is caused by an opportunistic infection of the thyroid gland by an organism which had been known to infect only the lungs of patients with AIDS.[29]

Poretsky’s other publications address a variety of subjects in diabetes and reproduction. Recent publications include an invited editorial in the Proceedings of the National Academy of Sciences on the role of advanced glycation end products (AGEs) in metabolic disease;[33] a study of the potential new treatment for prevention of diabetic nephropathy (carried out in collaboration with investigators from the Mount Sinai School of Medicine);[34] a review of the role of Vitamin D in human reproduction;[35] and an editorial on the problem of recurrent hospitalizations of patients with diabetes.[36]